Process for manufacturing pouches of ethylene copolymer film for containing a flowable material

ABSTRACT

A process for making pouches filled with a flowable material, using a vertical form, fill and seal apparatus, in which process each pouch is made from a flat web of film by forming a tubular film therefrom with a longitudinal seal and subsequently flattening the tubular film at a first position and transversely heat sealing said tubular film at the flattened position, continuously filling the tubular film with flowable material above said first position, flattening the tubular film above a predetermined quantity of flowable material at a second position and transversely heat sealing said tubular film at the second position, the improvement comprising making the pouch from a film comprising at least one layer formed from a blown film formed from a blend comprising a linear polymer of ethylene with at least one C 4 -C 10  alpha-olefin manufactured in a single-site catalyst polymerization process, and at least one of the following  
     a) a linear polymer of ethylene with at least one C 4 -C 10  alpha-olefin made by a multi-site catalyst polymerization process;  
     d) a high pressure low density polyethylene; and  
     c) additives selected from the group consisting of stabilizers, antiblock additives and extrusion aids;  
     and, the vertical form, fill and seal apparatus includes impulse sealing means for making transverse seals in the film through the flowable material.

RELATED APPLICATIONS

[0001] This application is a continuation of Ser. No. 08/732,533, filedOct. 15, 1996 pending which was a continuation of Parent applicationSer. No. 08/488,346 filed Jun. 12, 1995, now abandoned filed asapplication PCT/CA94/00571 on Oct. 13, 1994, all the disclosures ofthese applications being hereby incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The invention relates to films used to make pouches filled withflowable materials, e.g. liquids.

[0003] As used herein, the term “flowable material” does not includegaseous materials, but encompasses materials which are flowable undergravity or may be pumped. Such materials include liquids, e.g. milk,water, fruit juice, oil; emulsions, e.g. ice cream mix, soft margarine;pastes, e.g. meat pastes, peanut butter; preserves, e.g. jams, piefillings, marmalade; jellies; doughs; ground meat, e.g. sausage meat;powders, e.g. gelatin powders, detergents; granular solids, e.g. nuts,sugar; and like materials. The invention described herein isparticularly useful for flowable foods, e.g. milk.

BACKGROUND OF THE INVENTION

[0004] It is well known to package flowable materials, for example,milk, on a pouch-forming apparatus such as a so-called vertical form,fill and seal apparatus. Typically, using such an apparatus, a flat webof synthetic thermoplastic film is unwound from a roll and formed into acontinuous tube in a tube-forming section, by sealing the longitudinaledges on the film together to form a so-called lap seal or a so-calledfin seal. The tube thus formed is pulled vertically downwards to afilling station. The tube is then collapsed across a transversecross-section of the tube, the position of such cross-section being at asealing device below the filling station. A transverse heat seal ismade, by the sealing device, at the collapsed portion of the tube, thusmaking an air-tight seal across the tube. The material being packagedenters the tube above the transverse heat seal in a continuous orintermittent manner, thereby filling the tube upwardly from thetransverse heat seal. The tube is then allowed to drop a predetermineddistance usually under the influence of the weight of the material inthe tube. The jaws of the sealing device are closed again, thuscollapsing the tube at a second transverse section, which may be at,above or below the air/material interface in the tube, depending on thenature of the material being packaged and the mode of operation of theprocess. The sealing device seals and severs the tube transversely atthe second transverse section. The material-filled portion of the tubeis now in the form of a pillow shaped pouch. Thus, the sealing devicehas sealed the top of the filled pouch, sealed the bottom of thenext-to-be formed pouch and separated the filled pouch from thenext-to-be-formed pouch, all in one operation. Variations onpouch-forming machines and in particular on this type of vertical form,fill and seal apparatus are either known or conceivable. For example,the forming and sealing functions may be performed separately fromsevering function on separate machines. Also, the jaws of the sealingdevice could move to the next sealing position rather than have the filmdrop to the next position or there could be two sets of sealing jawsthat seal both transverse ends simultaneously. Further, instead offorming a tube, two pieces of film could be fed into the machine and thepouch could be made by four seals, two longitudinal and two transverse.

[0005] Examples of the vertical, form, fill and seal apparatus of thetype described above are the Prepac® IS-6 or IS-7 liquid packagingmachine.

[0006] A sealing device commonly used is a so-called impulse sealerwhich has a sealing element mounted in sealing jaws and electricallyinsulated therefrom. In operation, the sealing jaws are closed and anelectrical current is caused to flow through a sealing element, e.g. awire, for a fraction of the time that the jaws are closed. The jawsremain closed during a cooling or equilibration period, during which theseal forms, before the sealing jaws are opened. The syntheticthermoplastic film must be able to provide a transverse seal thatsupports the weight of the flowable material, e.g. liquid, in thenext-to-be-formed pouch. It is important that the cooling of the sealtakes effect before the weight of the liquid can weaken or rupture thebottom seal. Sealing may also be carried out using any other suitableheat-sealing apparatus.

[0007] In the operation of pouch-forming machines, it is known to usefilm made from a blend containing 70-90% linear ethylene/butene-1copolymer having a density of about 0.919 g/cm³ and a melt index ofabout 0.75 dg/min and 10-30% high pressure polyethylene, i.e. ahomopolymer, having a melt index of about 2 to 10 dg/min and a densityof from 0.916 to 0.924 g/cm³. Density is determined by ASTM ProcedureD1505-85 and melt index by ASTM Procedure D1238-90B (Condition E). Suchfilms having a thickness of about 76 micrometers, have been usedcommercially on vertical form, fill and seal apparatuses for makingpouches containing about 1.3 liters of milk. Pouches made from such filmtend to suffer from defective seals, i.e. a tendency to have weaktransverse end/and longitudinal seals even though the operatingconditions of the impulse sealer have been optimized. Defective sealsmay lead to the phenomenon known as “leakers”, in which the flowablematerial, e.g. milk, may escape from the pouch through pinholes thatdevelop at or close to the seal. It has been estimated that leakersaccount for about 1-2% of the 1.3 liter milk pouch production.

SUMMARY OF THE INVENTION

[0008] U.S. Pat. No. 4,521,437 of W. J. Storms, issued Jan. 4, 1985,discloses the use of pouches of ethylene/octene-1 copolymer film in thepackaging of flowable materials. That patent discloses that pouches madefrom the ethylene/octene-1 copolymer provide superior leakerperformance, i.e. a lower percentage of leakers, compared with relatedfilms described above that are formed from linear ethylene/butene-1copolymers.

[0009] It has now been surprisingly found that further improvements inleaker performance may be achieved using ethylene copolymersmanufactured using a single-site polymerization catalyst.

[0010] Accordingly, the present invention provides a film for makingpouches containing a flowable material, said pouch having at least twoheat sealed ends, said film being made from a composition comprising acopolymer of ethylene and at least one C₄-C₁₀ alpha-olefin manufacturedin a polymerization process using a single-site polymerization catalyst.

[0011] The present invention further provides a pouch containing aflowable material, said pouch having at least two heat sealed edges,wherein the film is made from a composition comprising a copolymer ofethylene and at least one C₄-C₁₀ alpha-olefin manufactured in apolymerization process using a single-site polymerization catalyst.

[0012] The present invention still further provides a process for makingpouches filled with a flowable material, using a vertical form, fill andseal apparatus, in which process each pouch is made from a flat web offilm by forming a tubular film therefrom with a longitudinal seal andsubsequently flattening the tubular film at a first position andtransversely heat sealing said tubular film at the flattened position,filling the tubular film with a predetermined quantity of flowablematerial above said first position, flattening the tubular film abovethe predetermined quantity of flowable material at a second position andtransversely heat sealing said tubular film at the second position, theimprovement comprising making the pouches from a flat web of film madefrom a composition comprising a copolymer of ethylene and at least oneC₄-C₁₀ alpha-olefin manufactured in a polymerization process using asingle-site catalyst.

[0013] Most particularly, the present invention provides a process formaking pouches filled with a flowable material, using a vertical form,fill and seal apparatus, in which process each pouch is made from a flatweb of film by forming a tubular film therefrom with a longitudinal sealand subsequently flattening the tubular film at a first position andtransversely heat sealing said tubular film at the flattened position,continuously filling the tubular film with flowable material above saidfirst position, flattening the tubular film above a predeterminedquantity of flowable material at a second position and transversely heatsealing said tubular film at the second position, the improvementcomprising making the pouch from a film comprising at least one layerformed from a blown film formed from a blend comprising a linear polymerof ethylene with at least one C₄-C₁₀ alpha-olefin manufactured in asingle-site catalyst polymerization process, and at least one of thefollowing

[0014] a) a linear polymer of ethylene with at least one C₄-C₁₀alpha-olefin made by a multi-site catalyst polymerization process;

[0015] b) a high pressure low density polyethylene; and

[0016] c) additives selected from the group consisting of stabilizers,antiblock additives and extrusion aids;

[0017] and, the vertical form, fill and seal apparatus includes impulsesealing means for making transverse seals in the film through theflowable material.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The film of the present invention preferably has a density in therange of 0.86 to 0.94 g/cm³ and a melt index of 0.2 to 10 dg/min andmost preferably has a density in the range of 0.88 to 0.93 g/cm³ and amelt index of 0.3 to 5 dg/min.

[0019] The ethylene copolymer made with single-site catalyst may beobtained using a variety of known polymerization processes for themanufacture of linear polyethylene including processes that operate insolution, in the gas phase or as a slurry process. Ethylene copolymersmade with the single-site catalysts are commercially available and maybe manufactured in accordance with processes disclosed in ModernPlastics, p. 15, May 1993, Plastics Focus Vol. 25, No. 12, Jun. 21, 1993and in Exxon Chemical Exact Facts, Vol. 1, February, 1993. By the term“single-site catalyst” is meant a metallocene or constrained geometrycatalyst. Metallocene catalyst are organometallic coordination compoundsobtained as a cyclopentadienyl (Cp) derivative of a transition metal ormetal halide. The metal is bonded to the Cp ring by electrons moving inorbitals extending above and below the plane of the ring (pi bond).Metallocene catalysts systems are extremely sensitive to the geometry ofthe catalytic site at the transition metal (the “single-site”). Examplesof single-site catalysts include Cp₂TiCl₂, Cp₂ZrCl₂, Cp₂HfCl₂,(C₅(CH₃)₅)₂TiCl₂, Ph₂Me(Ind)₂ZrCl₂, and[Me₄CpSi(Me)₂N(t-Bu)]TiCH₂[o-PhN(Me₂)], Cp₂Fe B(C₆F₅)₄.

[0020] The polyethylene obtained with the single-site catalystpreferably has a density in the range of 0.8 to 0.93 g/cm³, andespecially in the range of 0.88 to 0.91 g/cm³. In addition, the polymerpreferably has a melt index of less than 5 dg/min, particularly in therange of 0.3 to 2 dg/min and especially in the range of 0.5 to 1.5dg/min. Preferred polymers include ethylenelbutene-1, ethylene/hexene-1,ethylene-octene-1 and ethylene/hexene-1/butene-1 copolymers.

[0021] The composition used to make the pouches preferably furthercomprises at least one polymer selected from the group comprising alinear copolymer of ethylene and at least one C₄-C₁₀ alpha-olefin, ahigh pressure polyethylene and blends thereof. Preferably thecomposition comprises 10 to 100 parts by weight of a copolymer ofethylene and at least one C₄-C₁₀ alpha-olefin manufactured in apolymerization process using a single-site polymerization catalyst andfrom 0 to 90 parts by weight of at least one polymer selected from thegroup comprising a linear copolymer of ethylene and at least one C₄-C₁₀alpha-olefin, a high pressure polyethylene and blends thereof. Inparticularly preferred embodiments, the composition comprises 20 to 100and especially 50 to 100 parts of the copolymer obtained using thesingle-site catalyst, and conversely 0 to 80 and 0 to 50 parts of theother polymers specified above.

[0022] Processes for the manufacture of so-called high pressurepolyethylene from ethylene monomer have been operated commercially fordecades. A variety of such polymers are available. The high pressurepolyethylene preferably has a density of 0.916 to 0.93 g/cm, especially0.918 to 0.925 g/cm³. In addition, the high pressure polyethylenepreferably has a melt index in the range of 1 to 10 dg/min andespecially in the range of 1.5 to 5 dg/min.

[0023] Processes for the commercial manufacture of linear copolymers ofethylene and at least one C₄-C₁₀ alpha-olefin have been known for morethan thirty years. Such processes may be operated in solution, in thegas phase or as a slurry process. The catalysts used are frequentlybased on titanium and are referred to as coordination catalysts; suchcatalysts may also be described as multi-site catalysts or heterogeneouscatalysts. The polymer obtained is linear in nature, as opposed to thebranched nature of high pressure polyethylene. The C₄-C₁₀ alpha-olefinhydrocarbon comonomer is preferably at least one of butene-1, hexene-1or octene-1. The linear polyethylene preferably has a density in therange of 0.9 to 0.93 g/cm³, preferably 0.912 to 0.93 g/cm³ andespecially in the range of 0.918 to 0.925 g/cm³. In addition, thepolymer preferably has a melt index in the range of 0.3 to 10 dg/min,preferably 0.3 to 2 dg/min and especially in the range of 0.5 to 1.5dg/min.

[0024] The film may be used by itself to form the pouch or a part or acomposite film. The composite film may be a coextruded film, a coatedfilm or a laminated film. The film of the present invention could belaminated with the other films such as a nylon film, a polyester film, ametallized polyester film, an EVA copolymer film, or with a PVDCcoating. It could also be coextruded with, for example, an ethylenevinyl acetate copolymer.

[0025] In all of the pouches of the present invention, the film is atleast on the inside of the pouch. The end use for the pouch tends todictate, in a large degree, the selection of the other material ormaterials used in combination with the film. For example, nylon may beused in combination with the film of the present invention, forpackaging oleagenous substances, e.g. cooking oil, motor oil;polyvinylidene chloride (PVDC) or ethylene vinyl alcohol copolymers maybe used in combination with the film of the present invention where aflavour or aroma barrier is desirable. It will be appreciated by thoseskilled in the art that a composite film having a film only on theinside of the pouch would be sufficient for pouches made with alongitudinal fin seal, whereas a composite film having films on the twoouter layers of the composite film would be necessary for pouches madewith a longitudinal lap seal.

[0026] When composite films in which the two outer layers are the filmof the present invention, the two outer films may be made from the sameor different polymers or blends. Preferably, however, they are the samepolymers or blends. It is to be understood that the composite film mayconsist of two layers of the film of the present invention. This lattercomposite film is useful when one or both layers are, for examplecoloured with dyes or pigments, e.g. a layer having carbon black, ironoxide, aluminum, bronze powder or some other dark pigment and an outerlayer which contains a light pigment, e.g. titanium dioxide, zinc oxide.

[0027] The blends useful in the present invention may be made byblending the constituents prior to feeding to the hopper of a filmextruder, or may be made by blending the constituents at the time ofextrusion just prior to remelting in the extruder, or alternatively theconstituents may be melt blended in the extruder.

[0028] The ethylene/alpha-olefin copolymer or blend ofethylene/alpha-olefin copolymer, e.g. in pellet form, may be fed into afilm extruder and extruded into film form using known techniques. Onepreferred method of manufacturing film is the so-called blown filmprocess disclosed in Canadian Patent No. 460,963 issued Nov. 8, 1949 toE. D. Fuller. Another preferred method of manufacturing film uses aninternal or external cooling mandrel in the blown film process, asdisclosed, for example, in Canadian Patent No. 893,216 issued Feb. 15,1972 to M. Bunga and D. V. Thomas.

[0029] The film, after manufacture, is slit longitudinally intoappropriate widths. Where a vertical form, fill and seal apparatus isused, the width is selected on the basis of the diameter of the tube tobe formed.

[0030] It will be understood by those skilled in the art that additives,e.g. UV stabilizers, anti-block agents, slip additives, may be added tothe polymers from which the pouches of the present invention are made.

[0031] The pouches of the present invention may be used in the packagingof flowable materials, e.g. liquids, as defined above. In particular,the pouches may be used in the packaging of milk. The pouches may bemade using any liquid pouch-forming apparatus, including vertical form,fill and seal machines such as the Prepac® IS-6 or IS-7.

[0032] The films of the present invention may be used to make pouches ofimproved integrity as compared to prior art pouches, therebysubstantially reducing the leaker rate of the pouches. The leaker ratemay be measured using a drop test. In a drop test, pouches of the samedimensions containing the same type and amount of liquid are made usingthe same type of pouch-forming equipment and are all dropped from thesame height and position. The number of leakers expressed as apercentage of the total number of pouches dropped is used as the basisof comparison between pouches made from different films. The particulardrop test used in the Examples herein is referred to as the M₁₁-test.The M₁₁-test is carried out as follows: In general terms, the M₁₁-testis a drop test carried out on 1.3 liter water-filled pouches. In thetest, pouches containing 1.3 liters of water, at a temperature of 10±5°C., are made from a 32 cm. wide film web, on a Prepac® IS-6 verticalform, fill and seal machine. The water-filled pouches containing coldwater, are dropped onto a concrete floor from a height of 335 cm. Thepouches are positioned with the longitudinal axis of the tube, i.e.pouch, parallel to an imaginary vertical line.

[0033] Any pouch from which water flows or weeps after the pouch hasbeen dropped onto the floor, is termed a “leaker”. The number ofleakers, expressed as a percentage of the total number of pouchesdropped is the M₁₁-test value for the particular film being tested. Itwill be noted that the M₁₁-test value will be affected by the thicknessof the film as well as the material from which the film is made.

[0034] The process for forming the pouch with the Prepac® IS-6 machinefor the purpose of carrying out the M₁₁-test in the Examples is asfollows. The web of film is formed into a continuous tube with a lapseal, said tube having an inside diameter of approximately 9.8 cm.Atypical vertical sealing jaw of the Prepac® IS-6 apparatus has anapproximately 3.5 by 0.3 mm rectangular sealing wire made of Nichrome®alloy, and a transverse sealing jaw with an approximately 1.8 by 0.7 mmsealing wire made of Nichrome(t alloy. The operation of the vertical andtransverse sealing element should be optimized for the particular filmtype and thickness used. Typically, during vertical sealing of the tube,a 35-50 amp current at 14-24 volts is passed through the sealing wirefor about 0.2-0.5 seconds. The force applied by the vertical sealingjaws to the film is about 8 Newtons applied for a dwell time of about0.9 seconds. The vertical sealing jaw is cooled by water at 13±6° C.During transverse sealing of the tube, a 35-55 amp current at 10-15volts is passed through the sealing wire for about 0.2-0.5 seconds. Theforce applied by the transverse sealing jaws to the film is about 19 Napplied for a dwell time of about 0.9 second. The transverse sealing jawis cooled by water at 13±6° C. Both sealing jaws are covered with 150 μmthick glass fibre tape impregnated with Teflon® polytetrafluoroethyleneresin. With respect to optimizing the sealing operations, it will berecognized that the sealing conditions (e.g. amperage, voltage, dwelltime) depend on the thickness and melting characteristics of the film.For example, a 50 μm film would require lower amperage and voltage, ascontrolled by the rheostat on the apparatus, than would a 75 μm film.Typically such a change in film thickness requires an adjustment ofapproximately 10% of the rheostat range.

[0035] It is the film of the present invention that is selected upon thebasis of a drop test such as the M₁₁-test, not the composite film, wherethe film is coextruded or laminated with other film, and not the pouch.

[0036] The present invention is illustrated by the following examples.

EXAMPLE I

[0037] The following monolayer films were manufactured using aconventional blown film process and slit to a width of 324 mm, Film Abeing a comparative film:

[0038] A 85% of a (multi-site catalyst) linear low densityethylene/octene-1 copolymer, with a density of 0.920 g/cm³ and a meltindex of 0.75 dg/min; 15% of a high pressure low density polyethylene,having a density of 0.921 g/cm³, and a melt index of 5.0 dg/min;

[0039] B 85% of a linear low density ethylene/butene-1 copolymer,manufactured with a single-site catalyst, having a density of 0.900g/cm³ and a melt index of 1.2 dg/min commercially available from Exxon,sold under the trade name Exxon Exact 3028®; 15% of the low densitypolyethylene of A;

[0040] C 45% of the linear ethylene/octene-1 copolymer of A; 40% of alinear low density ethylene/butene-1 copolymer manufactured with asingle-site catalyst commercially available from Exxon, sold under thetrade name Exxon Exact 4011®, having a density of 0.887 g/cm3, a meltindex of 2.2 dg/min and a stress exponent of 1.08; and 15% of the lowdensity polyethylene of A. Each of the films has a thickness of 3 mil.

[0041] Each of the films were fed to a Prepac® IS-6 vertical form, filland seal pouch forming apparatus. Pouches having a vertical lap seal andtwo horizontal end seals were made, each being about 28 cm in length andcontaining 1.3 liters of water. The pouches obtained were droppedend-wise from a height of 335.3 cm onto a concrete floor in accordancewith the M₁₁-test. After dropping, each pouch was examined for leakers.

[0042] The results obtained were as follows: FILM NO. DROPPED NO.LEAKERS LEAKER % A 177 36 20.3% B 204 29 14.2% C 204 36 17.6%

[0043] This example shows that the pouches formed from the polyethylenemanufactured using a single-site catalyst (Films B and C) performedsignificantly better than the multi-site catalyst ethylene/octene-1copolymer (Film A).

EXAMPLE II

[0044] The procedure of Example I was repeated using the following filmswhich were made using an internal cooling mandrel in the blown filmprocess; Film D being a comparative film:

[0045] D 85% of a multi-site catalyst linear low densityethylene/octene-1 copolymer, with a density of 0.320 g/cm³, a melt indexof 0.75 dg/min and a stress exponent of 1.31; 15% of a high pressure lowdensity polyethylene, having a density of 0.921 g/cm³;

[0046] E 45% of a linear low density ethylene/octene-1 copolymermanufactured using a multi-site catalyst, as described in D; 40% of asingle-site catalyst linear ethylenelbutene-1 copolymer having a densityof 0.887 g/cm³, a melt index of 2.2 dg/min commercially available fromExxon sold under the trade name Exxon Exact 4011®; 15% of the lowdensity polyethylene of D;

[0047] F 65% of the linear low density ethylene/octene-1 copolymer of D;20% of the single-site catalyst linear ethylene/butene-1 copolymer of Eand 15% of the low density polyethylene of D.

[0048] The pouches were manufactured and dropped using the procedure ofExample I. The results obtained were as follows: FILM NO. DROPPED NO.LEAKERS LEAKER % D 204 39 19.1% E 203 29 14.3% F 204 32 15.7%

[0049] The results again showed the superior performance of the pouchesof the present invention.

EXAMPLE III

[0050] The procedure of Example I was repeated using the followingfilms, Film G being a comparative film:

[0051] G 85% of a multi-site catalyst linear low densityethylene/octene-1 copolymer, with a density of 0.920 g/cm³, a melt indexof 0.75 dg/min and a stress exponent of 1.31; 15% of a high pressure lowdensity polyethylene, having a density of 0.921 g/cm³, and a melt indexof 5.0 dg/min;

[0052] H 85% of a single-site catalyst-produced ethylene/hexene-1butene-1 terpolymer commercially available from Exxon sold under thetrade name Exxon Exact 3006® having a density of 0.910 g/cm³, a meltindex of 1.7 dg/min and a stress exponent of 1.07; 15% of a low densitypolyethylene of G;

[0053] I 45% of a multi-site catalyst linear low densityethylene/octene-1 copolymer; 40% of a single-site catalystethylene/butene-1 copolymer commercially available from Exxon, soldunder the trade name Exxon Exact 4011® having a density of 0.87 g/cm³, amelt index of 2.2 dg/min; 15% of a low density polyethylene of G.

[0054] The pouches were manufactured and tested using the procedure ofExample I. The results obtained were as follows: FILM NO. DROPPED NO.LEAKERS LEAKER % G 204 82 40.2% H 204 57 27.9% I 204 51 25.0%

[0055] The films of the invention showed significantly superiorperformance.

EXAMPLE IV

[0056] The procedure of Example I was repeated using the followingcomparative films:

[0057] L 85% of multi-site catalyst octene copolymer LLDPE, density0.920 g/cm³, melt index 0.75 g/10 min; 15% of a high pressurepolyethylene, density 0.921 g/cm³, melt index 5.0 g/10 min.

[0058] M 94% of a single-site catalyst octene copolymer LLDP, density0.915 g/cm³, melt index 1.02 g/l 0 min, commercially available from Dowunder the trade name Dow Affinity FM 1570®, 6% additive concentrates.

[0059] N 94% single-site catalyst octene copolymer LLDPE, density 0.908g/cm³, melt index 1.08 g/10 min, stress exponent 1.51 commerciallyavailable from Dow under the trade name Dow Affinity PL 1840®, 6%additive concentrates. FILM NO. DROPPED NO. LEAKERS LEAKER % L 204 6732.8% M 203 34 16.7% N 204 46 22.5%

EXAMPLE V

[0060] The following films were made using an internal cooling mandrelin the blown film process (otherwise the process of Example I was asfollows):

[0061] O 85% of a multi-site catalyst octene copolymer LLDPE, density0.920 g/cm³, melt index 0.75 g/10 min 15% of a high pressurepolyethylene, density 0.921 g/cm³, melt index 5.0 g/10 min.

[0062] P 30% of a single-site catalyst octene copolymer LLDPE, density0.915 g/cm³, melt index 1.02 g/10 min, commercially available from Dowunder the trade name Dow Affinity FM 1570®; 58% of a multi-site catalystoctene copolymer LLDPE, density 0.920 g/cm³, melt index 0.75 g/l 0 min;10% of a high pressure polyethylene, density 0.921 g/cm³, melt index 5.0g/10 min; and 2% of additive concentrates.

[0063] Q 94% of a single-site catalyst octene copolymer LLDPE, density0.915 g/cm³, melt index 1.02 g/10 min, commercially available from Dowunder the trade name Dow Affinity PL 1570®; and 6% of additiveconcentrates. FILM NO. DROPPED NO. LEAKERS LEAKER % O 204 80 39.2% P 20467 32.8% Q 204 51 25.0%

EXAMPLE VI

[0064] The following films were made using the process of Example V andthe procedure of Example I was followed:

[0065] R 85% of a multi-site catalyst octene copolymer LLDPE, density0.920 g/cm³, melt index 0.75 g/l 0 min; and 15% of a high pressurepolyethylene, density 0.921 g/cm³, melt index 5.0 g/10 min.

[0066] S 94% single-site catalyst octene copolymer LLDPE, density 0.903g/cm³, melt index 1.22 g/10 min, commercially available from Dow andsold under the trade name Dow Affinity PL 1880®; and 6% of additiveconcentrates.

[0067] T 94% of a single-site catalyst octene copolymer LLDPE, density0.908 g/cm³, melt index 1.08 g/10 min, commercially available from Dowand sold under the trade name Dow Affinity PL 1840®; and 6% of additiveconcentrates. FILM NO. DROPPED NO. LEAKERS LEAKER % R 203 85 41.9% S 21552 24.2% T 202 55 27.2%

[0068] The results show the improvement obtained using single-siteoctene copolymer LLDPE over multi-site octene copolymer LLDPE.

EXAMPLE VII

[0069] The films made in Examples I-VI were measured to determine theirdensity and melt index. The results are tabulated below: DENSITY(G/CUBIC MELT INDEX (G/10 EXAMPLE FILM CENTIMETRE) MIN) I A 0.919 0.7 B0.907 1.3 C 0.908 1.3 II D 0.918 0.7 E 0.909 1.3 F 0.914 0.9 III G 0.9230.7 H 0.916 1.4 I 0.911 1.3 IV L 0.921 0.9 M 0.916 1.1 N 0.911 1.2 V O0.918 0.7 P 0.917 0.8 Q 0.913 1.1 VI R 0.918 0.7 S 0.905 1.3 T 0.910 1.1

[0070] The invention may be varied in any number of ways as would beapparent to a person skilled in the art and all obvious equivalents andthe like are meant to fall within the scope of this description andclaims. The description is meant to serve as a guide to interpret theclaims and not to limit them unnecessarily.

1. A process for making pouches filled with a flowable material, using avertical form, fill and seal apparatus, in which process each pouch ismade from a flat web of film by forming a tubular film therefrom with alongitudinal seal and subsequently flattening the tubular film at afirst position and transversely heat sealing said tubular film at theflattened position, continuously filling the tubular film with flowablematerial above said first position, flattening the tubular film above apredetermined quantity of flowable material at a second position andtransversely heat sealing said tubular film at the second position, theimprovement comprising making the pouch from a film comprising at leastone layer formed from a blown film formed from a blend comprising alinear polymer of ethylene with at least one C₄-C₁₀ alpha-olefinmanufactured in a single-site catalyst polymerization process, and atleast one of the following a) a linear polymer of ethylene with at leastone C₄-C₁₀ alpha-olefin made by a multi-site catalyst polymerizationprocess; c) a high pressure low density polyethylene; and c) additivesselected from the group consisting of stabilizers, antiblock additivesand extrusion aids; and, the vertical form, fill and seal apparatusincludes impulse sealing means for making transverse seals in the filmthrough the flowable material.
 2. The process as claimed in claim 1,wherein the linear polymer of ethylene and at least one C₄-C₁₀alpha-olefin manufactured in a single-site catalyst polymerizationprocess is selected from the group consisting of ethylene/butene-1,ethylene/hexene-1, ethylene/octene-1 and ethylene/hexene-1/butene-1polymers.
 3. The process as claimed in claim 2, wherein the linearpolymer of ethylene and at least one C₄-C¹⁰ alpha-olefin manufactured ina single-site catalyst polymerization process contains no long chainbranching and is an ethylene/hexene-1 polymer.
 4. The process as claimedin claim 1, wherein the blend comprises: a) from 10 to 85% by weight ofa linear polymer of ethylene and at least one C₄-C₁₀ alpha-olefincontaining no long chain branching and manufactured in a single-sitecatalyst polymerization process, said polymer having a density in therange of from 0.8 to 0.93 g/cm3 and a melt index of less than 5 dg/min;b) from 0 to 75% by weight of a linear polymer of ethylene and at leastone C₄-C₁₀ alpha-olefin manufactured by a multi-site catalystpolymerization process, said polymer having a density in the range offrom 0.9 to 0.93 g/cm³ and a melt index of from 0.2 to 2 dg/min; and c)15% by weight of a high pressure low density polyethylene having adensity of from 0.9 to 0.93 g/cm³ and a melt index of from 1 to 10dg/min.
 5. The process as claimed in claim 1, wherein the linear polymercomprises a long chain branched linear polymer of ethylene and at leastone C₄-C₁₀ alpha-olefin manufactured in a single-site catalystpolymerization process.
 6. The process as claimed in claim 1, whereinthe long chain branched linear polymer has a density in the range of 0.9to 0.93 g/cm³ and a melt index in the range of 0.3 to 10 dg/min, and thehigh pressure low density polyethylene has a density in the range of0.916 to 0.93 g/cm³ and a melt index in the range of 1 to 10 dg/min. 7.The process as claimed in claim 1, wherein the film has a density in therange of from 0.86 to 0.94 g/cm³ and a melt index of from 0.2 to 10dg/min.
 8. The process as claimed in claim 5, wherein the blendcomprises 94% by weight of a single-site catalyst produced long chainbranched linear polymer of ethylene-octene having a density 0.915 g/cm³and melt index 1.02 g/10 min and 6% by weight of additives.
 9. Theprocess as claimed in claim 5, wherein the blend comprises 30% by weightof a single-site catalyst produced long chain branched linear polymer ofethylene-octene of density 0.915 g/cm³ and melt index 1.02 g/10 min; 58%by weight of a linear copolymer of ethylene-octene produced by amulti-site catalyst process of density 0.920 g/cm³ and melt index 0.75g/10 min; 10% by weight of a high pressure polyethylene of density 0.921g/cm³ and melt index 5.0 g/10 min; and 2% by weight of additives. 10.The process as claimed in claim 1, wherein the blend comprises 94% byweight of a single-site catalyst produced long chain branched linearpolymer of ethylene-octene having a density 0.908 g/cm³ and melt index1.08 g/10 min and 6% by weight of additives.
 11. The process as claimedin claim 1, wherein the blend comprises 94% by weight of a single-sitecatalyst produced long chain branched linear polymer of ethylene-octenehaving a density 0.903 g/cm³ and melt index 1.22 g/10 min and 6% byweight of additives.
 12. The process of claim 1, wherein the filmcomprises a layer containing dyes or pigments.